1. Field of the Invention
This invention relates generally to an exposure control system with inertia means for a photographic apparatus and more particularly to an exposure control system with a selectively presentable inertia characteristic for more precisely controlling the rate of effective aperture opening in a photographic apparatus.
2. Description of the Prior Art
Exposure control systems for photographic apparatus conventionally embody light weight shutter blade elements with scene light admitting apertures therethrough. Shutter blade elements of this type may be moved in directions which operate to progressively enlarge and decrease the effective scene light admitting aperture that is defined by the overlapping scene light admitting apertures. The rate at which the blade elements are moved determines the rate at which the effective aperture decreases and increases, and has a direct influence on the achievable depth of field. Thus, in order to increase the depth of field, it is desirable to precisely control the speed of the shutter blade elements as they are moved in the direction of progressively increasing effective aperture size. Such shutter blade elements are often moved toward the open position through the influence of a biasing spring, the output force characteristic of which controls the speed at which the shutter blade elements move. For exposure control systems embodying light weight shutter blade elements as well as other moving components, it is necessary to utilize a substantially light biasing spring to achieve the desired slow rate of shutter blade opening. However, in such a light weight exposure control system of the above-described type where the actuating force is small, the frictional forces between moving components becomes a significant part of the overall force which must be overcome by the biasing means. These frictional forces also tend to vary with shutter blade movement and thus cause a jerking movement of the shutter blades which is highly undesirable. An increase in the output force characteristic of the biasing spring by itself may make the opening movement of the shutter blade elements less sensitive to frictional force variations; however, the increased shutter blade speed will also limit the depth of field which could otherwise be achieved.
Other difficulties associated with exposure control systems of the above-described type may arise as a result of the shutter blade elements reaching their maximum effective aperture defining position and abruptly stopping. This abrupt stopping of the shutter blade elements may result in jarring or bouncing which would have a distorting effect upon the actual scene light pinging upon the film plane. The same problem may also arise when the shutter blade elements are returned to their closed position and then abruptly stopped so as to jar or bounce the individual shutter blade elements.
Therefore, it is a primary object of this invention to provide an exposure control system for a photographic apparatus wherein the rate of aperture opening may be uniformly determined without effecting the fast rate of aperture closing. The concept of an inertially influenced exposure control system to overcome the above described problems is disclosed in an application for U.S. Patent entitled "Inertial Means For Exposure Control System" by George D. Whiteside and Bruce K. Johnson, Ser. No. 574,695 filed May 5, 1975, in common assignment herewith.
Therefore, it is another primary object of this invention to provide an improved exposure control system of the above-described inertially influenced type.
It is also an object of this invention to provide an exposure control system featuring a pair of movable shutter blade elements having respective light admitting apertures therethrough which overlap in a manner defining an effective aperture wherein shutter blade movement toward an effective open aperture may be determined at a uniform rate without effecting the rapid closing of the shutter blade elements.
It is a further object of this invention to provide an exposure control system for photographic apparatus of the type featuring at least a pair of shutter blade elements having respective light-admitting apertures therethrough which overlap to define an effective aperture wherein the shutter blade elements may be moved to their maximum effective aperture defining position and stopped thereat without jarring or bouncing the individual shutter blade elements.
It is another object of this invention to provide an exposure control system for a photographic apparatus wherein the exposure control system is of the type embodying at least a pair of shutter blade elements movable in correspondence with each other by a walking beam wherein means are included for selectively presenting an inertia characteristic to the walking beam when moved from its light blocking position to a maximum effective aperture defining position.
It is an additional object of this invention to provide an exposure control system for a photographic apparatus wherein the various components of the exposure control system are automatically returned to their initial position in readiness for the commencement of a subsequent photographic cycle without jarring or bouncing the individual components of the exposure control system.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the mechanism and system possessing the construction combination of elements and arrangement of parts which are simplified in the following detailed disclosure.